The semiconductor device fabrication process uses plasma processing at different stages to make semiconductor devices. Plasma processing involves energizing a gas mixture by imparting energy to the gas molecules by introducing radio frequency (RF) energy into the gas mixture. This gas mixture is typically contained in a vacuum plasma chamber, and the RF energy is typically introduced into the plasma chamber through electrodes.
In a typical plasma process, the RF generator generates power at a radio frequency—which is broadly understood as being within the range of 3 kHz and 300 GHz—and this power is transmitted through RF cables and networks to the plasma chamber. In order to provide efficient transfer of power from the RF generator to the plasma chamber, an intermediary circuit is used to match the fixed impedance of the RF generator with the variable impedance of the plasma chamber. Such an intermediary circuit is commonly referred to as an RF impedance matching network, or more simply as an RF matching network.
In plasma applications, conditions can arise where voltage builds up within the plasma chamber such that an electric arc occurs inside the plasma chamber. The voltage buildup can occur between the electrodes or between any two surfaces within the plasma chamber. The electrical arc can result in damage to the surface of the material being processed or even cause damage to other surfaces inside the chamber. Methods have been employed to detect arcing and to either preventing arcing from occurring in the first place or to limit the damage caused by arcing, but these methods are slow and often fail to capture fast transients.
Thus, there is need for a more reliable method of controlling the plasma chamber and the power provided thereto to prevent arcing and/or limit the damage caused by arcing.